1. Field of the Disclosure
The present invention relates in general to storage media and, in particular, to a system, method and apparatus for shingled magnetic recording in disk drives.
2. Description of the Related Art
Disk drives such as magnetic or optical disk drives, read data from and write data to media disks. For example, hard disk drives having magnetic patterns on magnetic media have been used for decades to store digital data, and offer low cost, high recording capacity, and rapid data retrieval.
The magnetic material is made up of separate magnetic grains. The magnetic polarity within each grain is the same, e.g., each grain has for instance an upward or downward polarity in perpendicular recording. The recorded data bits include many of these separate grains. The read head is affected by the summation of the effects of the nearby grains as it passes through a data track. Nearby grains have a stronger magnetic effect than grains that are further away. In general, the magnetic flux diminishes by a factor of distance to the third power, so the magnetic grains directly below the read head element have the most profound effect on the readback signal.
The read head will always pick up some magnetic signal from adjacent tracks. This adjacent track interference (ATI noise) can be minimized by reading at the center of the data track such that the ATI noise is small in magnitude. If the read head is positioned too close to an adjacent track, then the adjacent track's magnetic bits provide a more significant portion of the readback signal (i.e., the “noise” becomes the dominant signal). There is a point where if the read head is too close to the adjacent track, the readback signal becomes unreliable to decode (e.g., jumbled or noisy). In these cases, the analog signal processing and error correction in the hard drive's read channel may not be able to separate the target track data from the adjacent track's data. Thus, improvements in magnetic recording continue to be of interest.